Impacts of land conversion and management measures on net primary productivity in semi-arid grassland

Ecological restoration measures implemented in China have profoundly impacted vegetation NPP. This study aimed to estimate the effects of the land conversion and management measures on the grassland ecosystem in semi-arid regions. Land use data were employed from 2000 to 2015 to compare land conversion and coverage changes in Xilingol grassland. Then, the contributions of land conversion and management policies were quantified by assessing the difference between actual NPP and climate-induced NPP changes. The results indicated that the grassland area had a net loss of 534.42 km(2), and the net area of increased vegetation coverage was 74,683.05 km(2). Furthermore, the total NPP increased by 8,010.73 Gg C center dot yr(-1) (1 Gg = 10(9) g), of which the human activities, including grazing management measures (+6,809.40 Gg C center dot yr(-1)) and land conversion (45.72 Gg C center dot yr(-1)) contributed to 85.58% of the increase in NPP. Transformation from desert and farmland dominated grassland expansion and NPP increase, while urbanization and desertification caused large grassland reduction and NPP loss. The grazing management increased vegetation NPP in most regions except for some regions in the desert steppe and the farming-pastoral zone. Related policies should be further adjusted to strengthen the management of the desert steppe and farming-pastoral regions.